filectx: fix cmp() of file starting with '\1\n'
If file data starts with '\1\n', it will be escaped in the revlog to
create an empty metadata block, thus adding four bytes to the size in
the revlog size index. There's no way to detect that this has happened
in filelog.size() faster than decompressing each revision [1].
For filectx.cmp(), we have the size of the file in the working directory
available. If it differs by exactly four bytes, it may be this case, so
do a full comparison.
[1]: http://markmail.org/message/5akdbmmqx7vq2fsg
Corrupt an hg repo with two pulls.
create one repo with a long history
$ hg init source1
$ cd source1
$ touch foo
$ hg add foo
$ for i in 1 2 3 4 5 6 7 8 9 10; do
> echo $i >> foo
> hg ci -m $i
> done
$ cd ..
create a third repo to pull both other repos into it
$ hg init version2
$ hg -R version2 pull source1 &
$ sleep 1
pulling from source1
requesting all changes
adding changesets
adding manifests
adding file changes
added 10 changesets with 10 changes to 1 files
(run 'hg update' to get a working copy)
$ hg clone --pull -U version2 corrupted
requesting all changes
adding changesets
adding manifests
adding file changes
added 10 changesets with 10 changes to 1 files
$ wait
$ hg -R corrupted verify
checking changesets
checking manifests
crosschecking files in changesets and manifests
checking files
1 files, 10 changesets, 10 total revisions
$ hg -R version2 verify
checking changesets
checking manifests
crosschecking files in changesets and manifests
checking files
1 files, 10 changesets, 10 total revisions